Quote:
Originally Posted by ha9981
Quote:
Originally Posted by GearKid
Quote:
Originally Posted by rantarM3
Perhaps they used the wrong rod cap (or opposite of how it should go), which may have misaligned the threads just enough for them to get stripped. They discovered the mistake, put the correct cap back on, and gave you a call. Just conjecture...
Don't they start the bolt by hand? I would be surprised if anyone would just put the bolt in and immediately hit it with an impact wrench. Surely they would have noticed that the threads were engaging farther into the rod. Threads are unlikely to be damaged on disassembly, especially when the upper threads are fine.
Another theory - someone used an OEM bolt, torqued it up, bolt snapped in the middle of the threads allowing that section of the bolt to spin and damage its threads as the upper part of the bolt prevented it from moving further into the rod.
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Here's my latest thought that may explain this stripped rod. Let's say a former owner swapped out the bearings at 45k or something like that. New OEM bearings and bolts go in. This rod and maybe the others were significantly over tightened. Maybe instead of 130 degrees they were tightened to 130Nm or ft-lbs. this was not enough to strip the threads initially but after running the motor for 30k miles the threads start to break loose. The rod holds together because the upper threads keep the bolt from pulling out. Everything stays tight until the current shop pulls it all apart and starts to tighten down that rod again. The tech gets only half way to spec when those threads completely fail.
If this is true then we may see similar issues as motors are opened up a second time. |
We know eccentricity is impacted by torque. If it really was torqued that high I would assume the bearings would show. It is why the correct torque is so important.
Did they inspect the cylinder for this rod? |
Right on. Funny thing is that the rod#8 bearings look normal for this motor. It's rod#7 that had the most wear. The #8 bearings (at first appearance) suggest the rod cap was bolted down correctly.